Significant gaps in HIV diagnosis rates, linkage to and retention in HIV care, timely antiretroviral therapy (ART) initiation, and viral load (VL) suppression among persons living with HIV (PLWH) undermine the potential impact of 'treatment as prevention' and jeopardize achievement of US National HIV/AIDS Strategy (NHAS) goals. There is a significant need for more rigorous evidence regarding the effectiveness of several promising intervention strategies, some of which are already being implemented alone or in combination. In late 2009, the NYC Department of Health and Mental Hygiene (DOHMH) began implementing a comprehensive Care Coordination Program (CCP) at 28 Ryan White-funded agencies, targeting patients at high risk for suboptimal care cascade outcomes. The CCP intervention combines various evidence-based programmatic elements into a package, including case management, patient navigation, directly observed therapy (DOT), structured health promotion in home/field visits, and outreach to assist patients in accessing needed care and related services. The purpose of this retrospective cohort study, led jointly by investigators from the CUNY School of Public Health at Hunter College and the NYCDOHMH, is to: 1) assess the effectiveness of the CCP intervention by comparing primary outcomes among CCP participants with those of similar PLWH in HIV care who do not receive the CCP intervention; 2) among those who enroll in CCP, identify individual and program-level determinants of care engagement and VL suppression up to 36 months following CCP enrollment; and 3) assess the cost-effectiveness (cost per quality-adjusted life year [QALY]) of the CCP relative to usual care outside the CCP, considering downstream cost-savings and individual and public health benefits due to improved VL suppression and HIV infections averted. We expect the proposed research to generate much- needed evidence related to the effectiveness, outcome determinants, and cost-effectiveness of a promising, scalable service delivery strategy, ultimately enabling HIV care programs to further evolve achieve the greatest possible uptake and impact.